Heating cable for extraction pipes of viscous hydrocarbons or paraffinic in conventional wells and type tight wells, vertical or directional, with  flooded annular in casual or permanent form, suitable for use between low and high fluid pressures ranges

ABSTRACT

A heating cable for an extraction pipe of viscous hydrocarbon or paraffinic in a well, the heating cable including a sleeve made of a flexible material, the sleeve has a perimeter, an internal cavity, and a continuous homogeneous length, the sleeve is free of perforations; electrically conductive conductors placed inside the sleeve, the electrically conductive conductors are parallel to each other and separate from each other by a space; a primary insulation layer independently wrapping each one of the electrically conductive conductors; a layer including of a single fluoropolymer material completely filling up the entire cavity of the sleeve and forming a solid structure that encases the electrically conductive conductors, the primary insulation layer, the entire space between the electrically conductive conductors, and the entire perimeter of the sleeve; a metallic shield surrounding the layer consisting of the single monolithic fluoropolymer material, the metallic shield has a shape of a ribbon; the heating cable is flat.

REFERENCE TO RELATED APPLICATIONS

This application is a continuation in part Application of U.S.application Ser. No. 15/700,137, filed Sep. 10, 2017, entitled HEATINGCABLE FOR EXTRACTION PIPES OF VISCOUS HYDROCARBONS OR PARAFFINIC INCONVENTIONAL WELLS AND TIGHT TYPE WELLS, VERTICAL OR DIRECTIONAL, WITHFLOODED ANNULAR IN CASUAL OR PERMANENT FORM, SUITABLE FOR USE BETWEENLOW AND HIGH FLUID PRESSURE RANGES, pending, which is a continuation ofU.S. application Ser. No. 14/249,847 filed Apr. 10, 2014, entitled,HEATING CABLE FOR EXTRACTION PIPES OF VISCOUS HYDROCARBONS OR PARAFFINICIN CONVENTIONAL WELLS AND TIGHT TYPE WELLS, VERTICAL OR DIRECTIONAL,WITH FLOODED ANNULAR IN CASUAL OR PERMANENT FORM, SUITABLE FOR USEBETWEEN LOW AND HIGH FLUID PRESSURE RANGES, abandoned, the content ofwhich is incorporated herein by reference, which claimed priority overArgentinean Application No. 20130101184, filed Apr. 12, 2013.

FIELD OF THE INVENTION

The present invention relates to a heating cable for extraction pipes ofviscous hydrocarbon or paraffinic in conventional wells and tight typewells, vertical or directional, with flooded annular in eventual orpermanent cases, suitable for use between low and high fluid pressureranges, the cable being flat with parallel electric conductors, withhigh operational flexibility.

The purpose of this heating type cable is to avoid and/or unblockobstructions in extraction well pipes for hydrocarbons caused by theaccumulation of substances, such as paraffin and hydrates, as well as toreduce the high oil viscosity rates, hindering the fluid removal,especially when this fluid is at the lower paraffin viscosity orprecipitation temperature values, lower than the suitable limit values,and exposed to high pressure, for example, over a 1000 psi and reachingmore than even the 10,000 psi.

BACKGROUND OF THE INVENTION

The prior art shows a special heating cable in which the heating effectis achieved by a short circuit between the core and one of the surfacelayers.

In addition, the prior art shows a heating cable which includes fiberoptic conductors. The fiber optic allows measuring the well'stemperature; and therefore, it is also used to detect fluid presence bythe temperature difference.

Also, the prior art shows a heating cable whose structure ispredominantly made of lead, intended to the three-phase power supplywhich is applied directly on the pipe. In the practice, this type ofcable has resulted in numerous faults, only tolerated low heating powersand required very high currents, therefore they are not suitable for oilproduction pipes of high viscosity or pressure.

The prior art shows a heater that is fixed onto the concrete walls ofnon-intubated wells.

In addition, the prior art shows a heat pump, which heats the intakemaking a short circuit between the pumping tree and the wall of the tubeproduction.

Finally, the prior art shows a heating cable for oil production pipescharacterized because it includes the combination of a thermo conductivemetal outer pipe and inner flexible cover with electrically insulatingproperties, anti-corrosive and mechanical strength properties, whereinthe cover is formed by a plurality of overlapped layers which includes:(a) first an electrically insulating inner layer which surrounds thepower electrical wires for the heater elements connected to theconductor along the device; (b) a second enmeshing metallic layer thatsurrounds the first layer; (c) a third polymeric layer that surroundsthe second layer; and (d) an outer shielding layer, which surrounds thethird layer. Although this heating cable, under certain conditions,properly meets its function, when it is subjected to high pressuresinside of the hydrocarbon production well, begins to have structural andfunctional deficiencies. It is to say, through the interstices of themetallic mesh, the high pressure causes deformation in the insulatinglayer that surrounds the electrical conductors, thus affecting thedielectric capacity of the insulation layer, which results even morenoticeably by the chemical effects of the fluid that is filtered betweenthe mesh and the insulating layer. In addition, the metallic mesh ispermeable to the radio frequencies, which, due to their own flow currentcan generate interference on other cables or instruments used in thewell.

With the current state of technology, it is common that the wells arebrought to exploitation limits that were before impossible, and is usualthat the wells are of high pressure, for example, the tight type ofwells of recent development in the world. All of this leads to allaccessories and elements used in the extraction should be moreresilient, so it is essential that the development of new elements ishighly resistant to high pressure and temperatures, as is the cable thatis the object of the present invention.

Advantages of the Invention

In the heating cable of the present invention, the number of layers thatdefine its structure with regard to the succession of layers of theconventional cables has been reduced, allowing to simplify themanufacturing process, lowering the time than the standard timeinvolved, and reducing the electric energy consumption of the requiredmaterials or supplies, all of which translates into lower cablemanufacturing cost.

Regarding the advantages in the use of this cable, it is worthmentioning, for example, that it is extremely suitable to withstand highpressure and temperatures without risk of leakage between the layersthat could damage its structure, such as is the case in conventionalcables, thus, increasing the cable service life, and maintaining theelectrical conductors insulated efficiently and protected even in thepresence of very high fluid pressure.

In the present invention the term “monolithic layer” means a solid layermade of a single strong material.

The structure of the monolithic (solid) layer of the fluoropolymermaterials gives the cable a great mechanical resistance to thecompression and, at the same time, a high dielectric coefficient withoutfissures, which gives a high reliability and a wider range of operation.Also, these structural features provide a greater resistance toreinstallation operations arising from “pulling” operations, usually inwells and particularly critical in horizontal or directional wells byhigh mechanical exposure of them.

The particular design of this invention makes it small enough to enterin very tight tubing—casing combinations that no other systems in theindustry can do. Also require lower currents for high power which makethe application easier to feed with standard field power sources. It isparticularly suited to new high-pressure wells that use thosecombinations like Non-Conventional wells Tight or Shale. It is also veryuseful when used in “in liner” installations in horizontal or deviatedwells, no matter if they are Conventional or Non-Conventional. The lineris smaller than the casing and in general the space available to installanything inside a liner is very limited. The small section required toinstall this heater makes it the best option when liners are small (from5″ to 7″) without compromising oil flow or power output.

The particular structure of the heater makes it also very simple tomodify, adapt or repair, thereby maintaining the low profile and alsoits operational safety.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a heating cable forextraction pipes of viscous hydrocarbon or paraffinic in conventionalwells and tight type wells, vertical or directional, with flooded ringin eventual or permanent cases, suitable for use between low and highfluid pressure ranges. This cable, of flat type with parallel electricconductors, is also suitable for use in both vertical and directionalwells, with high operational flexibility in a wide range of variables.Each one of the electric conductors is covered by a primary insulationlayer, and the assembly thereof is monolithically coated by a maininsulating layer of fluoropolymer material resistant to the highpressure of the surrounding fluid. Outside of the main insulating layer,the cable structure is complemented with an external shield defined by athin layer of metallic material.

The invention relates to a heating cable for an extraction pipe ofviscous hydrocarbon or paraffinic in a well, the heating cable includinga sleeve made of a flexible material, the sleeve has a perimeter, aninternal cavity, and a continuous homogeneous length, the sleeve is freeof perforations; electrically conductive conductors placed inside thesleeve, the electrically conductive conductors are parallel to eachother and separate from each other by a space; a primary insulationlayer independently wrapping each one of the electrically conductiveconductors; a layer including a single fluoropolymer material completelyfilling up the entire cavity of the sleeve and forming a solid structurethat encases the electrically conductive conductors, the primaryinsulation layer, the entire space between the electrically conductiveconductors, and the entire perimeter of the sleeve; a metallic shieldsurrounding the layer consisting of the single monolithic fluoropolymermaterial, the metallic shield has a shape of a ribbon; the heating cableis flat.

BRIEF DESCRIPTION OF THE DRAWINGS

For greater clarity and understanding of the present invention, it isillustrated in several figures where it is represented according to thepreferred embodiments, for example, where:

FIG. 1 is a cross-sectional view of the heating cable;

FIG. 2 is a partial cross-sectional perspective view of a section of theheating cable;

FIG. 3 shows, as an example of application of the heating cable, asection of the hydrocarbons extraction pipe on which are fixed thethermo conductive conductors in which interior extends the cable; and

FIG. 4 shows a cross sectional view showing the thermo conductiveconduits attached to a rod located in the interior of the productionpipe.

DETAILED DESCRIPTION OF THE INVENTION

In FIGS. 1 and 2 can be seen that the heating cable 1 object of thepresent invention. The heating cable 1 is flat and includes:

A sleeve 1 a made of a flexible material. The sleeve 1 a has aperimeter, an internal cavity, and a continuous homogeneous length. Thesleeve 1 a is solid and free of perforations.

Electrically conductive conductors 2 are placed inside the sleeve 1 a.The electrically conductive conductors 2 are parallel to each other andseparated by a space.

A primary insulation layer (3) independently wraps each one of theelectrically conductive conductors 2.

Each conductor will be individually protected in order to increase theoperational safety.

The insulating layer consisting of a single element insulating materialneeds to be flexible yet very resistant to outer pressure (crushing) andat the same time maintain an extremely high dielectric value. Thisconsideration is based on the fact that such layer is thin and will beexposed to pressure, high temperatures, and eventually to aggressivechemicals if the outer layer is damaged. In such case, It will act as asecond barrier of defense and will maintain the heater in operationuntil a pulling activity may allow to repair it.

Using a single material makes it simpler and fulfills the requiredcharacteristics. Using different layers of different materials may seembetter but that adds a complexity that in the end goes against the finalobjective. A failure probability increases whit the use of more layers.In general, several layers are used when you cannot achieve thedifferent characteristics with only one. For example, adding a metalclad to increase mechanical resistance. (That is not needed in thepresented design)

That increases failure probability, increases size (which is critical asexplained in uses with tight spaces) and also increases cost andcomplicates or voids repair possibilities.

A layer consisting of a single fluoropolymer material (4) completelyfills up the entire cavity of the sleeve 1 a and forms a solid structure(monolithically) that encases the electrically conductive conductors 2,the primary insulation layer (3), the entire space between theelectrically conductive conductors 2, and the entire perimeter of thesleeve 1 a.

The single fluoropolymer material (4) is resistant to the high pressureof the surrounding fluid.

Filling completely the entire cavity of the sleeve 1 a with the singlefluoropolymer material (4) provides a solid structure having theelectrically conductive conductors 2 that gives the heating cable agreat mechanical resistance to the compression and, at the same time, ahigh dielectric coefficient without fissures, which gives a highreliability and a wider range of operation.

Different fluoropolymers may be but not all of them are suitable tofulfill all requested variables. For example, Polytetrafluoroethylene(PTFE) can withstand higher temperatures but it is not hard enough forthe application. Others may cover one of the required characteristicsbut not all of them at the same time.

One of the preferable fluoropolymers may be Ethylene tetrafluoroethylene(ETFE). The ETFE provides the necessary strength while maintaining ahigh dielectric insulation and excellent chemical resistance.

In one embodiment, the present invention uses Polyether ether ketone(PEEK). The PEEK is a non-fluorinated polymer option that will betechnically suitable, but cost it is considerably higher.

An external shield (5) is placed outside the solid layer (4). Theexternal shield (5) is made of a thin layer of a metallic material. Theexternal shield (5) may be, for example, in the form of a ribbon woundaround the fluoropolymer material (4).

On the example of the preferred embodiment, which is described andillustrated, the electrical conductors 2 are multifilament conductors.

In another preferred embodiment, the cable 1 includes three lines ofconductors 2 which correspond to each one of the phases of thethree-phase power applied.

FIG. 3 shows a typical hydrocarbons extraction pipe 6 which is placed ina production well, on which are fixed, heat exchangers and thermoconductive metallic conduits 7, through support devices having anchors 8and clamps 9. Throughout the conduits 7, the heating cable 1 of thepresent invention is extended.

FIG. 4 shows an alternative use of the cable 1, in the practice, thethermo conductive conduits 7 can be attached, for example, to a rod 10located in the interior of the production pipe 6 in positionsubstantially coaxial with the mounting and fastening devices (8,9). Inthis way, the thermo conductive conduits 7 with the cable 1 inside, willdefine a direct heat exchange medium with the fluid transported by theproduction pipe, it is worthy to say that without the duct 5 being incontact with the inner wall of the production pipe, but directly withthe circulating fluid within it.

The heating cable may include a flexible sleeve; and

a solid core placed inside the flexible sleeve;

the solid core includes solid layer consisting of a single fluoropolymermaterial and encasing a plurality of electrically conductive conductorsthat are individually wrapped with a primary insulation layer and ametallic shield surrounding the layer consisting of the singlemonolithic fluoropolymer material;

wherein the electrically conductive conductors are parallel to eachother and separate from each other by a space.

Having thus particularly described and determined the nature of thepresent invention and how it is to be realized, is claimed, in exclusivethe right and property.

1. A heating cable for an extraction pipe of viscous hydrocarbon or paraffinic in a well, the heating cable comprising: a sleeve made of a flexible material, the sleeve has a perimeter, an internal cavity, and a continuous homogeneous length, the sleeve is free of perforations; electrically conductive conductors placed inside the sleeve, the electrically conductive conductors are parallel to each other and separate from each other by a space; a primary insulation layer independently wrapping each one of the electrically conductive conductors; a layer consisting of a single fluoropolymer material completely filling up the entire cavity of the sleeve and forming a solid structure that encases the electrically conductive conductors, the primary insulation layer, the entire space between the electrically conductive conductors, and the entire perimeter of the sleeve; a metallic shield surrounding the layer consisting of the single fluoropolymer material, the metallic shield has a shape of a ribbon; wherein the heating cable is flat.
 2. The heating cable comprising: a flexible sleeve; and a solid core placed inside the flexible sleeve; wherein the solid core includes solid layer consisting of a single fluoropolymer material and encasing a plurality of electrically conductive conductors that are individually wrapped with a primary insulation layer and a metallic shield surrounding the layer consisting of the single monolithic fluoropolymer material; wherein the electrically conductive conductors are parallel to each other and separate from each other by a space.
 3. A heating cable for an extraction pipe of viscous hydrocarbon or paraffinic in a well, the heating cable comprising: a thermo conductive conduit; and a heating cable including: a sleeve made of a flexible material, the sleeve has a perimeter, an internal cavity, and a continuous homogeneous length, the sleeve is free of perforations; electrically conductive conductors placed inside the sleeve, the electrically conductive conductors are parallel to each other and separate from each other by a space, a primary insulation layer independently wrapping each one of the electrically conductive conductors, a layer consisting of a single fluoropolymer material completely filling up the entire cavity of the sleeve and forming a solid structure that encases the electrically conductive conductors, the primary insulation layer, the entire space between the electrically conductive conductors, and the entire perimeter of the sleeve, a metallic shield surrounding the layer consisting of the single fluoropolymer material, the metallic shield has a shape of a ribbon, wherein the heating cable is flat; wherein the flat cable passes through the thermo conductive conduit; wherein the thermo conductive conduit secured to a rod located inside an extraction pipe; wherein the rod and the thermo conductive conduit are not in contact with inner walls of the extraction pipe, but in direct contact with the fluid transported inside the extraction pipe. 